The Collaborative International Dictionary of English v.0.48:

Inauspicious \In`aus*pi"cious\, a.
   Not auspicious; ill-omened; unfortunate; unlucky;
   unfavorable. "Inauspicious stars." --Shak. "Inauspicious
   love." --Dryden. -- In`aus*pi"cious*ly, adv. --
   In`aus*pi"cious*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

inauspicious
    adj 1: not auspicious; boding ill [syn: inauspicious,
           unfortunate] [ant: auspicious]
    2: contrary to your interests or welfare; "adverse
       circumstances"; "made a place for themselves under the most
       untoward conditions" [syn: adverse, inauspicious,
       untoward]
    3: presaging ill fortune; "ill omens"; "ill predictions"; "my
       words with inauspicious thunderings shook heaven"-
       P.B.Shelley; "a dead and ominous silence prevailed"; "a by-
       election at a time highly unpropitious for the Government"
       [syn: ill, inauspicious, ominous]

Moby Thesaurus II by Grady Ward, 1.0:

102 Moby Thesaurus words for "inauspicious":
   apocalyptic, bad, badly off, baleful, baneful, black, bodeful,
   boding, criminal, dark, depressed, dire, donsie, doomful, dreary,
   evil, evil-starred, fatal, fateful, foreboding, fortuneless,
   funest, gloomy, hapless, ill, ill off, ill-boding, ill-considered,
   ill-fated, ill-omened, ill-seasoned, ill-starred, ill-timed,
   improper, in adverse circumstances, inaccurate, inappropriate,
   inconvenient, inexpedient, infelicitous, inferior, inopportune,
   intempestive, intrusive, invalid, irrelevant, late, lowering,
   luckless, mal a propos, malapropos, malevolent, menacing, mistimed,
   of evil portent, off base, ominous, out of line, out of luck,
   out of phase, out of time, peccant, planet-struck, portending,
   portentous, premature, sad, short of luck, sinful, sinister,
   somber, star-crossed, threatening, too late, too soon, unbefitting,
   unblessed, underprivileged, unfavorable, unfit, unfitting,
   unfortunate, unhandy, unhappy, unhealthy, unkind, unlucky,
   unpleasant, unpromising, unpropitious, unprosperous,
   unprovidential, unready, unripe, unseasonable, unskillful,
   unsuitable, untimely, untoward, vicious, wicked, wrong